AMplify: Episode 5, Dr Mark Eldridge

Kim McKay: Welcome to the Australian Museum's podcast AMplify, I'm Kim McKay the director and CEO at the Australian Museum, the nation's first museum. Today I have the great privilege of interviewing one of our top research scientists, Dr Mark Eldridge. Mark is principal research scientist here in the mammalogy collection, and let me tell you, I think he's got one of the best jobs in the world because he gets to work with Australia's unique species. Welcome Mark.

Mark Eldridge: Thank you.

Kim McKay: Now, you've been at the Australian Museum I think since 2007 in this role, but before that tell us what you were up to.

Mark Eldridge: Before I came here I worked at Macquarie University, so I was teaching genetics and mammal courses there.

Kim McKay: Now, for the public, you were teaching genetics and mammal courses. We don't think they go together but they do now, don't they.

Mark Eldridge: Well, they do, particularly with new technology coming along, we can answer so many questions about mammals' history and indeed lives today by using genetics.

Kim McKay: So when you were a little boy growing up, I think in Murwillumbah in New South Wales, was it? Were you on a farm or were you in town or…?

Mark Eldridge: We were in town but we were on the edge of town, so just across the road was bush and then it was farmland and the river and all the rest, so there was plenty of opportunity to explore and be out in nature most of the time.

Kim McKay: So what sort of wildlife was hanging out in Murwillumbah back then?

Mark Eldridge: Well, Murwillumbah means 'place of many possums', and there are indeed lots of possums…

Kim McKay: Does it really; the place of many possums?

Mark Eldridge: Yes.

Kim McKay: Fantastic.

Mark Eldridge: So yes, lots of birds, lots of mammals. So I had very broad interests as a kid.

Kim McKay: So what did you do, did you just go out watching them or did you collect any or…?

Mark Eldridge: No, I was just wandering around really, just observing, watching, seeing what you could see, like most kids, just poking around getting into trouble.

Kim McKay: Well, it's good fun as a kid to poke around in the Australian bush, that's for sure, and getting into trouble too, I think it's par for the course. So you went to Murwillumbah high school, and did you study science then?

Mark Eldridge: Yes, I did, chemistry and biology at Murwillumbah High, and I found that pretty interesting, so I thought I'd do a science degree, and one thing led to another and here I am.

Kim McKay: So where did you do your undergraduate work?

Mark Eldridge: At Macquarie University.

Kim McKay: Right, so you sort of stayed there over time. And what was your PhD in?

Mark Eldridge: My PhD was in rock wallabies, which I'm still working on, trying to work out really how the different species had formed because they are quite an interesting group.

Kim McKay: They sure are. In fact, I should say at the Australian Museum you're quite a legend because you are Mr Rock Wallaby, aren't you.

Mark Eldridge: Yes, I have a bit of a reputation.

Kim McKay: Well, we'll get to those rock wallabies in a moment, but I think one of the most interesting things is that the Australian Museum, because it has this vast collection, and many species of course which are now extinct are held here at the museum, it enables scientists like yourself to delve into that collection in a new way, the new technology. Can you tell us a bit about how that happens?

Mark Eldridge: Yes, so with the new techniques we now only need really small pieces of DNA, and what is present in the museum collection is material that we used to call degraded, and now it's actually the perfect size to do genetic analysis, and so we are able to actually look at the DNA of pretty much all the specimens in the museum and answer questions that we could only ever dream about previously.

Kim McKay: So what have you discovered in that process?

Mark Eldridge: Well, we've discovered new species, we've discovered how the species have evolved in Australia, how they've moved around the landscape. We've answered all sorts of questions about the history of marsupials.

Kim McKay: So that must be a pretty exciting moment as a scientist when you discover a new species in the collection, is it?

Mark Eldridge: It is, I think it's one of the biggest thrills, is to come across and recognise something as different that no one else has recognised before, and you see it with fresh eyes and think, wow, I'm the first person to actually see this for what it is.

Kim McKay: So give me an example of when that most recently happened to you?

Mark Eldridge: Well, we were working with some rock wallabies in northern Australia, and the…

Kim McKay: Whereabouts were you?

Mark Eldridge: We were working around Litchfield and Kakadu, and then further across in the Kimberley.

Kim McKay: Right, so up in the Northern Territory. Litchfield National Park is a fabulous park, not far from Darwin in fact if anyone is in Darwin any time they can just drive down the road literally. Kakadu, a bit further but a very, very special place, but also up in the Kimberley. So this type of rock wallaby is spread right throughout the north-west of Australia, is it?

Mark Eldridge: Yes, well, that's what we thought but when we actually looked at the DNA we realised that there were two species here, one in the Northern Territory and one in the Kimberley, and they had been separated for a very long time, for millions of years. They were clearly different species but no one had actually pieced that together before and realised it.

Kim McKay: So, our identity is so wrapped up in these mammals, isn't it, these special Australian mammals. We grow up learning about them at school but in fact we are not the only country that has marsupials and monotremes, are we.

Mark Eldridge: No, New Guinea has actually more species of monotreme than we have…

Kim McKay: Really?

Mark Eldridge: Yes, they've got three species of echidna, for example, we've got just the one. And South America has a really big marsupial fauna, lots of things they call opossums over there which are found right through South America and up into North America.

Kim McKay: But they don't have a platypus, do they?

Mark Eldridge: No, they don't have monotremes. There are some fossil evidence that monotremes occurred many millions of years ago in South America…

Kim McKay: Really? What, sort of fossilised bones have been found, or what's been found?

Mark Eldridge: Yes, in Patagonia they found some teeth of a platypus-like creature.

Kim McKay: Patagonia is such a goldmine for fossils, isn't it, for dinosaur bones, so that's fantastic, so at some point, what, 60,000 years ago…?

Mark Eldridge: 60 million years ago.

Kim McKay: 60 million I should say! 60,000, that's no time at all. 60 million years ago the platypus saw its relative existed in Patagonia. Wow.

Mark Eldridge: Yes, that's right, and that's part of that whole Gondwanan heritage that we have of a shared fauna between Australia, Antarctica and South America.

Kim McKay: Exactly. Pretty exciting to be in that space and understand it, it's like piecing a jigsaw puzzle together really, isn't it.

Mark Eldridge: It is, you had this giant jigsaw puzzle, not just at the continental scale but also within the continent, looking at how mountains have come and gone and how species have moved around.

Kim McKay: But Australia was fortunate, we got these special species that hopped around, or koalas in trees that no one else has.

Mark Eldridge: That's right, we have this vast array of marsupials that are found nowhere else, so it's a real privilege to work on them.

Kim McKay: Now, I want to talk to you about some work you've done recently with the eastern quoll because if you've lived in Sydney a long time, you know that quolls used to be in backyards, pre-bandicoot days. I grew up with bandicoots under the cubby house, but there were quolls as well. And in fact I think the last spotted quoll was found in Vaucluse in Sydney, wasn't it.

Mark Eldridge: That's right, in Nielsen Park in Vaucluse there was quite a well-known colony of eastern quolls, and it was thought that this was the place that the eastern quoll made its last stand on the Australian mainland, but they used to be really common and people had them in backyards. That all changed in the early 1900s.

Kim McKay: Did they eat them?

Mark Eldridge: They didn't eat them, no…

Kim McKay: So it wasn't part of the Indigenous diet either, the Aborigines didn't eat them in Australia?

Mark Eldridge: Not as far as I know, no.

Kim McKay: Right, but they were certainly very much part of the landscape. Where does a quoll dwell?

Mark Eldridge: Well, they have a little den site that they go into during the day, a hollow log or under some rubbish or something, but then during the night they come out to forage on small invertebrates and small vertebrates, so lizards and mice and things like that.

Kim McKay: What is extraordinary is you've discovered a new version of this eastern quoll, perhaps the same one, recently, is that right?

Mark Eldridge: Yes, well it was thought to be extinct in the Australian mainland and the last specimen from 1963. And then last year we were contacted by National Parks and they had been given this specimen by a local resident in the Barrington Tops area, and it looked like an eastern quoll but they wanted to do some DNA testing to see whether it really was a mainland eastern quoll.

Kim McKay: So, for listeners, the Barrington Tops is where, how far from Sydney?

Mark Eldridge: It's about four hours drive north of Sydney, so up in the mountains, a very beautiful area, a very rugged and remote area, but yes, quite high elevation.

Kim McKay: So this eastern quoll was seen in 1990, and then you've tested the DNA.

Mark Eldridge: So we tested the DNA from it and then we compared it to DNA from specimens in our collection, which we knew were mainland eastern quolls, and the DNA was very close, so they were very similar to…in fact to some of the quolls from the Vaucluse and quite different from the eastern quolls in Tasmania. So we concluded that in all probability this was actually an eastern quoll from the mainland but decades after everyone thought it had gone extinct. So there was one still one running around in 1990, maybe there still is one still running around out there.

Kim McKay: Are you going up there?

Mark Eldridge: Well, we are trying to get some funding to go up there and put out cameras and have a look and see what we can find.

Kim McKay: So in this day and age, apart from being technologically astute dealing with DNA, you have to know how to operate cameras to capture the movements of these night-time creatures too.

Mark Eldridge: Well, camera trapping is another of these innovations that have come along that has revolutionised the way we do mammalogy. So many people use it now as a first point of seeing what's out there.

Kim McKay: Yes, it makes the expedition a whole new experience because you can share it with other people as well.

Mark Eldridge: That's right, and you can bring back pretty cute pictures of animals as well as data.

Kim McKay: So we hear words like phylogeny and taxonomy. What do they really mean?

Mark Eldridge: Well, phylogeny is piecing together the relationships between species, so it's actually looking at who is related to who and when they diverge from each other, so it's like building a family tree of all the different species going back through time and we can use DNA to do that and we can work out the relationships. Taxonomy is the more formal process of classifying things according to the system that Linnaeus set up hundreds of years ago now where you actually formally name things. So taxonomy is the science of naming things.

Kim McKay: The science of naming things but of course something that museums have been known for. We are the institutions globally that practice taxonomy. It's not a lost art or science but it's practised less now maybe than before.

Mark Eldridge: It is practised less now than before, which is a bit of a concern because there's still an awful lot of things to discover and name, but it is certainly a niche that the museum really fills very well.

Kim McKay: But a big part of your work is conservation biology, isn't it, this is why we investigate these species in Australia, we're concerned about their future and ensuring…helping to ensure that more species don't go extinct. So how does that work, the practical application of your studies?

Mark Eldridge: Because we are looking at DNA we are able to identify species and individuals, we are able to look at populations and how individuals move around the landscape in time, and so we do spend a lot of time advising national parks and other management agencies about how to manage populations, which ones to mix, which ones to keep separate, when are they becoming inbred and they need some new blood in them, and all those sorts of things.

Kim McKay: How is climate change impacting on our marsupials and other mammals?

Mark Eldridge: There is evidence that some mammals are retreating up slope, and some alpine specialists seem to be becoming less common. But yes, there's going to be huge impacts right across the board on our mammal fauna.

Kim McKay: So Australia's biodiversity is going to be probably significantly impacted as the climate warms.

Mark Eldridge: I think it will, and species are going to have to move to keep track with their habitat and their preferred climatic niche. And because we've fragmented the landscape, then sometimes these species actually can't move and now and so we are going to have to manage things much more deliberately and maybe even move animals around the landscape in a way that we haven't had to do before. Your distribution is going to be moving south, we're actually going to have to pick up animals and move them south because they can't actually get there themselves anymore.

Kim McKay: So, extreme intervention to manage our biodiversity.

Mark Eldridge: It will be extreme intervention but the alternative is extinction which I think is infinitely worse.

Kim McKay: Infinitely worse, yes, and of course because our fauna is so wrapped up in our psychology I think, our coat of arms. And in fact you wrote the macropod section, didn't you, on the Handbook of the Mammals of the World, which is…tell us what a macropod actually is.

Mark Eldridge: Well, a macropod, and yes, the big-feet macropod, it's the kangaroos and wallabies and rat kangaroos all fit into that whole group, so that group of animals that the rest of the world think is really weird because they hop, which is actually a weird thing for a big animal to do. Australians think that's reasonably normal because kangaroos hop, but biologically speaking it's a very, very odd way of getting around. So that very distinctive group of animals is the one that I wrote that section on, trying to summarise basically everything we knew about every species of macropod there was.

Kim McKay: So you are pretty much our world expert on macropods here at the Australian Museum.

Mark Eldridge: Well, I know an awful lot, particularly after reading thousands of papers on the macropods.

Kim McKay: I bet. That's right, people sometimes think science is all in the lab, but it's actually doing a review of all of the other scientific journals and papers that have been written, isn't it.

Mark Eldridge: That's right, yes.

Kim McKay: The literature review.

Mark Eldridge: The great literature review. And yes, there were piles and piles of papers in my office for months.

Kim McKay: I can only imagine. But what a great contribution you've made, Mark, to our understanding of Australian species. I really do believe that here at the museum we are so fortunate that we have exposure to this because it does set us up for why Australia is a special country and why we need to look after our landscape even more. What's the thing you take away every day, the passion that keeps making you come back here day in, day out? What is it?

Mark Eldridge: Well, it's the thrill of discovery, but more than that it's just an appreciation for how amazing Australia really is, and every day you learn something new about how animals have survived in this continent for a very long time, and yes, trying to do your bit to make sure they can continue to survive.

Kim McKay: Fantastic. Well, Mark Eldridge, thank you so much, and thank you as well for being part of the fantastic Australian Museum Research Institute where we do this great work to protect and preserve our species for the future.

And you've been listening to AMplifyat the Australian Museum, we'll talk to you next time. I'm Kim McKay, signing off.